I was teaching the day the airplanes hit the World Trade Center. It was the second meeting of “The Communist Manifesto for Seminarians,” a course for my fellow graduate students. By the time I got to class, both towers had collapsed. A few hours later, Building 7 came down as well. We dispensed with a planned discussion about what Marxists mean by “idealism” and “materialism” and talked instead about the meaning of this particular example of the “propaganda of the deed.”

We already sensed that, with George W. Bush and Dick Cheney in the White House, the attacks would mean war. But like the rest of the world, we didn’t yet have the faintest idea how long that war would last. And 16 years on, we still don’t know.

A few years later, I found myself in front of 40 undergraduates on the first day of the first ethics course I would ever teach. You know how sometimes you have no idea what you’re going to say until the words are out of your mouth? That day, I opened my mouth and this came out: “I was so excited about this class that I couldn’t sleep last night.” Eighty horrified eyes stared back at me. “I guess it wasn’t like that for you,” I added, and felt the blush creep up my face. Most of them had the grace to laugh.

Thirteen years later, I still have trouble sleeping the night before a new semester begins. It’s not exactly stage fright, but knowing that I’ll only have a few chances to convince a new crop of students that they really do want to examine their deepest values -- the things they care most about -- and even talk about them in front of their peers.

In fact, most of them do care deeply and about important things, too, like how they should treat their friends, their parents, and their sexual and/or romantic partners. They care about their friends who drink and drug too much and appreciate the friends who get them home safe when they do the same. They care about economic inequality, especially when they’re trying to find a place they can afford to rent in this city of soaring prices, San Francisco, or when contemplating the massive debt most of them will be carrying for years, if not a lifetime, after they graduate.

Some of them regularly turn out to be Milton Friedman-style economic libertarians. Almost invariably, more are reflexively anti-capitalist. More than half of them are young people of color. They and the majority of their white peers care deeply about racism. They don’t think the police should shoot unarmed black men and they tend to believe that people of color face institutional barriers that white people never even see. Slavery, they know, was a terrible idea, but many of them are fuzzy about when it started in this country and how it ended.

Quite a few of them are immigrants or the children of immigrants. Some are undocumented or DACA recipients, so not surprisingly they care about immigration laws and policies. Their fellow students would never turn them in to the authorities. They may not know exactly why, but they have the feeling it would be unethical.

Some of them are in the Reserve Officer Training Corps, or ROTC. Some are veterans. U.S. military adventures affect them directly. While the rest of the students do care about war and peace, most of their lives are touched more lightly by America’s wars than were those of their peers a decade ago.

The first hint I got about the gaps in my students’ background knowledge came early on in my teaching career. In a homework assignment a student wrote that Aristotle had quoted Shakespeare. Another thought that when that Greek philosopher mentioned a theater, he was talking about going to the movies.

I wasn’t surprised that those students knew little about ancient Athens; there’s no reason to expect them to arrive at college versed in Greek philosophy. But something far more basic was missing: a sense of the sweep of what Americans call “western” history -- a chronological grid on which to pin the key movements and events that shape today’s world. I soon found myself putting a giant timeline on the blackboard on which the students would try to place the authors we were reading. Then we’d fill it in with other world events.

Even the relatively short history of the United States occupies a strangely flattened state in many of their imaginations. In their minds, for instance, all of the country’s wars -- especially those of the twentieth century -- seem to run together, making it hard to understand how one war can lead to another.

My pre-collegiate history education was not really much better than theirs, but it was somewhat different. I grew up in Washington, D.C., in the days when Congress ran the city directly, including defining the curriculum for elementary and secondary school students. We were required to take three cracks at American history (in fifth, eighth, and twelfth grade). Repeatedly, we spent so much time on the 13 original colonies that, by the day school let out for the year, we had barely reached World War I. I never did find out what happened after that, not in school anyway. Nowadays, schools have speeded things up a bit and the war they never get to happened in Vietnam.

I’m certainly not the first person to discover that, for new generations, foundational events in her own life -- the Civil Rights movement, the Vietnam War, the women’s liberation movement, even the first Gulf War -- are, to the young, history almost as ancient as the Civil War. Why should they know about such things? They weren’t even born yet.

But here’s a surprising development -- surprising because this last decade and a half seems to have flown past so quickly. I’m now encountering students who have no memory of an event that has shaped their lives, this country, and much of the world for the last 16 years: the 9/11 attacks.

The Early Years

The first undergraduates I taught were already in their teens on 9/11, which meant that those attacks formed a historic dividing point in their lives. For them, as for the coterie of men who would lead this country to the “dark side” (to use Vice President Dick Cheney’s admonitory phrase), there was a “before 9/11 and an after 9/11.”

After 9/11, they lived in a nation “at war.” The United States was suddenly fighting an enemy that, as Defense Secretary Donald Rumsfeld told “Meet the Press” less than a month after the attacks, “is not just in Afghanistan. It is in 50 or 60 countries and,” he added, “it simply has to be liquidated.” Little did they -- or the rest of us -- know that the liquid this protean enemy most resembled was a blob of mercury, which multiplies into hundreds of separate droplets when you hit it.

Recently, former CIA director and retired general David Petraeus admitted to Judy Woodruff of the PBS NewsHour that the war on terror’s first battlefield, Afghanistan, has become the locus of a “generational struggle,” one that more than a decade and a half later is not “going to be won in a few years.”

I’ve watched that generational struggle as it developed in the classroom. My first students had friends and relations fighting in Afghanistan and Iraq. One young woman’s uncle, a man in his late forties, was a surgeon who had been “reactivated” and sent to Iraq years after completing his active service. In fact, it turns out that everyone who joins the military signs on for eight years, whether they know it or not. Any of those years not spent on active duty or in the “drilling” Reserves still leaves you in the “Individual Ready Reserves,” as many were surprised to discover when the U.S. Army ran short of personnel to fight two simultaneous land wars.

A few students had partners fighting overseas and their worry was painful to observe. Soon enough, I had women students whose male partners were returning from those wars as changed -- and dangerous -- men. Several confided (either to me privately or to an entire class) that they’d had to move out because they feared for their safety.

And soon one of our school’s graduates, Jennifer Moreno, died in combat.

Every September, the Army would appear on campus. Arriving in gleaming Hummers, they’d erect a portable climbing wall and pass out glossy recruitment literature, encouraging students to join ROTC. Once, I was stunned by the courage of four young women, who stood off to the side of the show holding up homemade antiwar signs. Then one fall, the recruiters didn’t show up at all. I never knew whether it was because the wars had fallen out of favor with the board of my Jesuit university or because troop drawdowns had eased recruitment pressure. All I knew was that it probably wasn’t thanks to those brave students with their hand-drawn signs.

In the early years, more than one ROTC member admitted to me (or our class) that he or she doubted the Bush administration’s rationale for the war in Iraq. One young man from Guam explained that, having accepted a scholarship (“my ticket off the island”), he was duty-bound to fight in Iraq despite his doubts. “I know that in basic training, they try to take you apart as a person and then put you back together as a soldier,” he told me. “I want you to know that I’m not going to let that happen to me.” I’ve often wondered what did happen to him.

Here’s another thing I remember from those early years. To my surprise, many of my students supported torture -- less as an interrogation method than as punishment for truly heinous crimes (torture, that is, as righteous vengeance). Terrorists should be tortured, some argued, as payback for 9/11, but perhaps because their own childhoods were still so near in time and memory, a number of them thought that those most deserving of torture were not political terrorists, but child abusers.

Just about all of them were certain of one thing: the men who flew the planes on 9/11 were Iraqis.

When Johnny (and Janie) Come Marching Home Again...

Eventually, of course, war veterans began to appear in my classes. They were older and in many cases more mature than the other students in ways that didn’t just reflect their age. I often teach an ethics class in which students work with a community-based organization. One veteran chose to do this “service learning” with Swords to Plowshares, which provides services for vets. They’d helped him when he first got out, and he wanted to return the favor. “If anyone tells you they came back whole from Iraq or Afghanistan,” he assured me, “they’re either lying or they just don’t know yet.”

He was right, I think. One thing I’ve noticed over the years: like many survivors of war, those vets never volunteer to talk about what they’ve seen. Nor do their fellow students show much curiosity about it, and I don’t ask directly. But some, like the young man who’d served five years as a sniper in Iraq and Afghanistan, are clearly in pain. He’d suffered a broken back and brain trauma when an improvised explosive device blew up his Humvee. He was bitter about the war and his own role in it, certain that he’d been lied to by his government. Since leaving the military he had learned a lot of history. Now, he sat in the last row of the classroom, back to the wall, one leg bouncing uncontrollably up and down. Usually he left early. The anxiety of being in a room with that many people, he explained to me, was more than he could endure.

Such veterans, however, are classroom oddities, rare exceptions to the general rule that the U.S. can fight an endless war on terror without pain, sacrifice, or even, in recent years, much attention at all. These days, my students live in a country that has been at war almost since they were born, and yet, as is true with most of their fellow citizens, the fighting could be happening on Mars for all the impact it has on them. Most of them no longer know people directly affected. Their friends and family, of course, aren't among the tens of millions of Iraqis, Syrians, Afghans, or Yemenis made refugees by those American wars and their consequences.

Most of them haven’t yet realized that, if their government hadn’t spent $5.6 trillion and counting on those very wars, there might have been federal money available to relieve them of the school debt they will carry for decades.

Those Who Fail to Learn...

It’s not an accident that my students arrive at college with little understanding of U.S. history or, for that matter, knowledge of how their government works. Nor is it their fault. Education is crucial to citizenship in a democracy and, for many years, those on the right in this country have done their best to defund and dismantle public education. Under President Trump we have a secretary of education who makes no secret of her belief that, like other public goods, education is best left in the tender hands of the market.

The other day I asked my “Ethics: War, Torture, and Terrorism” class to name the countries where the United States is currently involved in some military action. They were able to come up with Iraq and Afghanistan. A veteran then added Djibouti, where U.S. Africa Command has a key base. “Syria?” someone wondered. A ROTC member mentioned Yemen. No one even thought of Somalia or Libya. No one had heard of the West African country of Niger, where Sergeant LaDavid Johnson died in an ambush set by an ISIS affiliate. (If asked, some might have remembered that when Donald Trump called Johnson's widow, he made news by struggling to remember her husband’s name and suggesting that Johnson had known “what he signed up for.”)

Nor could they name any of the other countries, 76 in all, affected in some fashion by their country’s undeclared, never-ending “generational” war on terror.

The good news is that they want to learn.

The bad news: nowadays, they tend to think that the men who flew those planes on 9/11 were from Iran.